Since moving to Denmark, Princess Mary has focused on causes close to her heart, including sustainability.

"I believe that in order to find solutions to some of the most pressing global challenges of today we need to take a holistic approach that requires us to consider the social, environmental and economic aspects and work together in new and innovative partnerships, maybe with people and organisations we wouldn’t have thought about working with before," she told Vogue in 2016.

The royal pretended to struggle to open the beer before taking a sip. (AAP)

"It will require a continuous effort and patience, and strong and authentic leadership: it takes time to create real and sustainable change."

The Danish royal said she tries to use her platform to be as effective as possible when it comes to those causes, including the empowerment of women and their human rights.

WATCH: The five most Aussie things about Princess Mary. (Post continues.)

The royal couple will travel to Australia in October where they'll join the Duke and Duchess of Sussex at the Invictus Games from October 20 to 27. Also arriving for the Invictus games will be David and Victoria Beckham.